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E.H. Van Aken, L. Derycke, H. Charif, T. Luider, R. Cornelissen, M. Veckeneer; Non–Enzymatic Pharmacologic Vitreolysis by Beta–Aminopropionitrile (BAPN) . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4473.
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To investigate the possibility of pharmacologic vitreolysis in a non–enzymatic way. Lysyl oxidase is an extracellular enzyme that deaminates peptidyl lysyl residues involved in the cross–linking of fibrillar collagen. BAPN is a selective inhibitor of the lysyl oxidase enzyme. We studied the influence of BAPN on the fibrillar structure of the vitreous.
Eyes of 8–day old chick embryos were removed and injected with different concentrations of BAPN (0 mM, 0.1 mM, 0.5 mM, 1 mM). After 7 days ex vivo incubation at 37°C, 16/24 eyes were fixed for analysis by light microscopy and transmission electron microscopy. The remaining eyes were dissected and the vitreous was removed, lysed and prepared for SDS–polyacrylamide gel electrophoresis and analysis by fourier transform mass spectrometry.
The vitreous of eyes injected with 0.1 mM or 0.5 mM BAPN contained slightly fragmented collagen II fibrils on electron microscopic sections, compared to eyes that were injected with saline solution alone. The 1 mM treated eyes however showed clear fragmentation of collagen II fibrils. For mass spectrometry, a 200 and 160 kD band, representing collagen α1(II) chains, was selected for every condition, and treated with trypsin. The spectra of lysates of eyes treated with 0.1 or 0.5 mM BAPN were very comparable to the spectrum of the lysate of eyes that were injected with saline solution alone, or with the spectrum of a lysate of pure collagen II. The spectrum of lysates of eyes treated with 1 mM BAPN showed an effect on the up– and downregulation of specific peptides.
The vitreous of 8–day old chick embryos treated with 1 mM BAPN, was fragmented as shown by transmission electron microscopic sections. Mass spectrometry confirmed the specific alteration on protein expression with 1 mM BAPN. Our results suggest that administration of BAPN to vitreous of chick embryos reduces cross–linking of proteins in the vitreous.
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